https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:20583 Sat 24 Mar 2018 07:55:36 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:31030 4 with N2O, particularly at higher CH₄ conversions. For this purpose, key process variables, such as temperature (300 °C–550 °C) and a molar feed ratio (N₂O/CH₄ = 1, 3, and 5), were altered to establish the conditions for maximized H₂ yield. The experimental study was conducted over the Co-ZSM-5 catalyst in a fixed bed tubular reactor and then compared with the thermodynamic equilibrium compositions, where the equilibrium composition was calculated via total Gibbs free energy minimization method. The results suggest that molar feed ratio plays an important role in the overall reaction products distribution. Generally for N₂O conversions, and irrespective of N₂O/CH₄ feed ratio, the thermodynamic predictions coincide with experimental data obtained at approximately 475 °C–550 °C, indicating that the reactions are kinetically limited at lower range of temperatures. For example, theoretical calculations show that the H₂ yield is zero in presence of excess N₂O (N₂O/CH₄ = 5). However over a Co-ZSM-5 catalyst, and with a same molar feed ratio (N₂O/CH₄) of 5, the H₂ yield is initially 10% at 425 °C, while above 450 °C it drops to zero. Furthermore, H₂ yield steadily increases with temperature and with the level of CH₄ conversion for reactions limited by N₂O concentration in a reactant feed. The maximum attainable (from thermodynamic calculations and at a feed ratio of N₂O/CH₄ = 3) H₂ yield at 550 °C is 38%, whereas at same temperature and over Co-ZSM-5, the experimentally observed yield is about 19%. Carbon deposition on Co-ZSM-5 at lower temperatures and CH₄ conversion (less than 50%) was also observed. At higher temperatures and levels of CH₄ conversion (above 90%), the deposited carbon is suggested to react with N₂O to form CO₂.]]> Sat 24 Mar 2018 07:34:52 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:30564 2O conversion reactions within a temperature range of 300–600°C. These reactions were examined in a fixed bed tubular reactor. ZSM-5 (Si/ Al = 15), TS-1, and amorphous silicates were used as catalyst supports for cobalt loadings. All catalysts were prepared by following standard methods and recipes. In general, cobalt loading on supports was varied between 0.78 and 5.40 wt.-% (as determined from inductively coupled plasma (ICP) analysis). ICP, temperature programmed desorption, X-ray diffraction, and N₂ adsorption/desorption isotherms were used for the characterization of prepared catalysts. Cobalt on ZSM-5 support generates weak and strong acid sites. Furthermore, for the Co-ZSM-5 catalyst, prepared by a wet deposition method, the N₂O decomposition reaction is first order with an activation energy of ~132 kJ mol⁻¹. Co²⁺ and Co³⁺ are the suggested active species for the N₂O conversions in the studied range of temperatures.]]> Sat 24 Mar 2018 07:23:55 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:18679 Mon 20 Jul 2015 17:34:13 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:48260 ) and heat treatment on the physico-chemical properties of bovine bone powder. For this purpose, raw and alkali treated samples were heated separately at temperatures of 400 °C, 600 °C, 800 °C, and 1000 °C. A combination of characterization techniques, such as TGA, XRD, N2-adsorbtion isotherms, and EDX were used. It was found that the boiling of cleaned solid pieces of bones in 2 molar Ca(OH)₂ solution results in a mass loss of about 10 % (mainly discards oily liquid). TGA analysis affirms that the hydrocarbons of bone matrix are partially extractable (~ 10 %) in the boiling alkaline solution. The color of raw and treated bone samples remained similar, that is changing from yellowish white to grayish black before turning into white over temperatures ranging from 30 °C (room temperature), 400 – 600 °C, and 800 – 1000 °C, respectively. Moreover, XRD signatures were also comparable at unified temperature ranges, however, it was noted that carbonization due to heating engenders a significant change in the intensities of the x-ray reflections. Despite of having similarities, surface area of raw and treated bones at 400 °C, 600 °C and 800 °C were found to be different, indicative of a chemical interactions of calcium ions with bone. Quite interestingly, TGA, XRD, and N₂-adsorbtion isotherms support the argument that a limited amount of calcium ions diffuses into the vacancies or interstitial sites of bone lattice. Furthermore, EDX analysis of the samples calcined at 1000 °C confirms that the Ca(OH)₂ treatment increases the total calcium content of hydroxylapatite (inorganic part of bone matrix).]]> Mon 13 Mar 2023 14:46:37 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:36460 Mon 11 May 2020 13:20:44 AEST ]]>